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Re: [avr-gcc-list] eeprom problems

From: Theodore A. Roth
Subject: Re: [avr-gcc-list] eeprom problems
Date: Mon, 29 Sep 2003 21:38:47 -0700 (PDT)

On Tue, 30 Sep 2003, Jack Valmadre wrote:

:)I'm writing a program that writes a lot of information to EEPROM at the start 
then accesses it later on in the program.
:)I have used the <avr/eeprom.h> include file.
:)For every line that has an eeprom_write_byte() or and eeprom_read_byte() 
command, I get an error saying:
:)warning: passing arg 1 of `eeprom_write_byte' makes pointer from integer 
without a cast
:)Here is one example of each command:
:)eeprom_write_byte(10, 6);
:)PORTD = eeprom_read_byte(front_sensors);
:)How can I fix this?

Consider this contrived example:

-- begin example --
#define EEPROM __attribute__((section(".eeprom")))

struct eeprom_map
        uint8_t id;
        uint8_t len;
        char name[256];

struct eeprom_map ee_map EEPROM;

main (void)
        uint8_t len;
        char name[256];

        len = eeprom_read_byte (&ee_map.len);
        eeprom_read_block (name, ee_map.name, len);

        /* Do something interesting with name. */
-- end example --

Note that the prototypes of eeprom_{read,write}_byte are given as such:

  extern uint8_t eeprom_read_byte (const uint8_t *addr);
  extern void eeprom_write_byte (uint8_t *addr, uint8_t val);

While you are using this:

  eeprom_write_byte(10, 6);

The number 10 is an integer, you need to make it a pointer to uint8_t. How 
to do that is left as an exercise for the reader.

Ted Roth

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